LOANS AND LEASES (Schedule of Loans Outstanding, by Type of Loan) (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2020	Dec. 31, 2019
Total loans		$ 4,862,684	$ 4,394,137
Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		100.00%	100.00%
Unallocated Financing Receivables [Member]
Total loans		$ 272	$ 349
Unallocated Financing Receivables [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		0.01%	0.01%
Residential Mortgage [Member] | Residential Portfolio Segment [Member]
Total loans		$ 525,994	$ 549,138
Residential Mortgage [Member] | Residential Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		10.82%	12.50%
Multifamily Property [Member] | Residential Portfolio Segment [Member]
Total loans		$ 1,178,494	$ 1,210,003
Multifamily Property [Member] | Residential Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		24.23%	27.54%
Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans		$ 761,910	$ 761,244
Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		15.67%	17.32%
Commercial Loans Including Equipment Financing [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans	[1]	$ 2,285,382	$ 1,756,477
Commercial Loans Including Equipment Financing [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	[1]	47.00%	39.97%
Construction [Member] | Commercial Portfolio Segment [Member]
Total loans		$ 3,515	$ 5,306
Construction [Member] | Commercial Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		0.07%	0.12%
Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member]
Total loans		$ 54,006	$ 57,248
Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		1.11%	1.30%
Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other Loans [Member]
Total loans		$ 53,111	$ 54,372
Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other Loans [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)		1.09%	1.24%

[1] The June 30, 2020 balance includes PPP loans of $521.6 million